1. Field of the Invention
This present invention generally relates to laser scanning systems for reading data in the form of indicia such as bar code symbols on articles and, more particularly, to reading such indicia on surveillance tags removably mounted on the articles.
2. Description of the Prior Art
Various types of scanning systems are known in the prior art that are able to read bar code symbols. Bar code symbols are applied to the surface of an article in order to represent data which can be read by a scanner. The data may be used to identify the article or other characteristics thereof. The bar code symbol itself is a coded pattern of indicia comprised of a series of bars of various widths, spaced apart from one another to bound spaces of various widths.
Various types of desk-top or portable, hand-held scanner systems are exemplified by U.S. Pat. Nos. 4,369,361; 4,387,297; and 4,409,470--all of such patents being owned by the assignee of the instant invention and being incorporated by reference herein. Such scanners have generally been designed to operate at a certain working or reading distance from the symbol at a hand-held or stationary position.
Typically, a scanner includes a light source such as a laser or semiconductor device that generates a light beam. The use of semiconductor devices as the light source in scanner systems is especially desirable because of their small size, low cost and low power requirements. The light beam is optically modified, typically by a lens, to form a beam spot of a certain size. It is preferred that the beam spot size be approximately the same as the minimum width between regions of different light reflectivity, i.e., the bars and spaces of the symbol. The relative size of the bars and spaces is determined by the type of coding used, as is the actual size of the bars and spaces. The number of characters per inch represented by the bar code symbol is referred to as the density of the symbol.
The light beam is directed by optical components along a light path toward a target that includes a bar code symbol an the surface. A scanning component is also disposed in the light path. The scanning component may either sweep the beam spot across the symbol and trace a scan line across and past the symbol, or scan the field of view of the scanner or do both. A scanner also includes a sensor or photodetector. The photodetector has a field of view which extends across and slightly past the symbol and functions to detect light of variable intensity reflected off the symbol. The photodetector generates electrical signals representative of the sequences of bars and spaces in the symbol. The electrical signals are then decoded into data descriptive of the symbol.
Various types of electronic article surveillance systems are also known in the prior art. Such systems are used to prevent shoplifting and similar unauthorized removal of articles from a controlled area. More particularly, such systems provide a specially designed tag or label which is attached to the article. The tag or label contains active or passive electronic circuitry or a magnetic media which is responsive in a certain manner to an external electromagnetic field. When the article containing an activated tag or label is passed through a controlled exit, an alarm will be set off. In order to authorize the removal of the article from the control area, the tag or label must be either removed or deactivated by an authorized person. The present invention relates more particularly to surveillance systems that require deactivating of the tag, and to apparatus for deactivating a surveillance tag for authorized removal of the article from the controlled area.
In one surveillance system known in the prior art, sensor-emitter labels or tags contain a semiconductor diode and are applied to articles for the purpose of surveillance. For deactivating such tags, various devices are known in the prior art including, among others, radio frequency generators for burning out the diode. However, such generators are generally high powered and are coupled inductively to the tags by way of an R. F. field.
Another surveillance system involves the use of tags containing ferrite material that can be magnetized or demagnetized by a suitable magnetic field which alters the operating characteristic of the tag, thereby deactivating the same.
There are various devices known in the prior art for deactivation of a surveillance tag. U.S. Pat. No. 4,318,090 discloses a hand-held probe having spaced contacts that are arranged to be applied to and drawn along the surface of a surveillance tag that contains a diode. When the probe contacts engage exposed terminals of the diode, a high current is passed through the diode sufficient to destroy its conducting characteristics and thereby deactivate the tag.
There are a few systems in the prior art which combine both bar code reading and deactivation of surveillance tags. U.S. Pat. No. 4,141,078 discloses an automated library circulation control system for processing library books. The system includes at least one terminal having an optical reader for book identification, and an electromagnetic activator at each terminal for magnetizing and demagnetizing a magnetic strip in each book.
In operation, a book is placed in a book tray at each terminal, and a bar coded label on each book is read by an overhead optical scanner. The book is oriented in the book tray at the terminal with the label facing up and the spine of the book facing the front. The scanner reads a nine digit number on the label and generates signals representing the bar code which are thereupon transferred to a computer.
The electromagnetic activator is operable at about the same time (col. 1, lines 58 and 59) to activate or deactivate the magnetic strip in the book. The activator is located under the book tray and is operative on command from the computer. Failure of a user to deactivate the strip before taking the book from the library will activate an alarm at the library exit.
In all known prior art proposals, no light-reflective, coded indicia are associated with the surveillance tag itself. Either there is no confirmation of the tag removal for the system or such confirmation must depend on less reliable, user-dependent procedures.
Further, there are no know prior art proposals in which a surveillance tag having a coded indicia is associated with specific articles, and where the removal of the tag is enabled only where the specific article has been purchased or has been irrevocably selected for purchase.
Still further, there are no know prior art proposals where the coded indicia is displayed on a liquid crystal display, and where the code indicia is dynamically changeable.